This invention relates generally to dishwashers, and, more particularly, to dishwasher system fine filter systems.
Known dishwasher systems include a main pump assembly and a drain pump assembly for circulating and draining wash fluid within a wash chamber located in a cabinet housing. The main pump assembly feeds washing fluid to various spray arm assemblies for generating washing sprays or jets on dishwasher items loaded into one or more dishwasher racks disposed in the wash chamber. Fluid sprayed onto the dishwasher items is collected in a sump located in a lower portion of the wash chamber, and water entering the sump is filtered through one or more coarse filters to remove soil and sediment from the washing fluid. At least some dishwasher systems further include a fine filter system in flow communication with the main pump assembly to remove soil and sediment of a smaller size than those filtered by the coarse filters. The main pump assembly draws wash fluid from the sump to re-circulate in the wash chamber, and the coarse and fine filters are used to continuously filter the water in the sump during the re-circulation process.
At least one known fine filter assembly includes a fine filter having a filter screen disposed over a top of a filter body, and a pressure relief opening in the filter screen to prevent excessive pressure buildup in the fine filter body when the filter screen becomes clogged. This pressure relief opening, however, presents a potential continuous leak in the fine filter system, and further is vulnerable to re-entry of soiled fluid into the wash system
In an exemplary embodiment, a fine filter assembly for a dishwasher includes a filter body, a filter screen coupled to the body, and a pressure relief tube coupled to the body. The pressure relief tube includes a substantially vertical portion having an open top, and the pressure relief tube forms a standpipe that regulates pressure in the filter body when the fine filter is used. Wash fluid flows into the pressure relief tube from the fine filter until a column of fluid in the relief tube balances the operating pressure in the fine filter assembly. As pressure in the fine filter assembly increases, so does a height of the fluid column in the vertical portion of the pressure relief tube. Pressure may be regulated in the fine filter assembly up to a maximum pressure determined by the height of the vertical portion of the pressure relief tube. When the maximum pressure is exceeded, wash fluid flows through the open top of the vertical tube, thereby maintaining a relatively constant pressure in the fine filter assembly at or near the maximum pressure.
The vertical portion is distanced from the filter body and from the filter screen, and more specifically is located adjacent a vertical wall of a dishwasher tub in use. Due to the location of the vertical portion of the pressure tube, and further because the open top of the pressure tube is located a distance above the bottom of the tub, the pressure relief tube is less vulnerable to soiled water re-entry into the system. Moreover, the vertical portion of the pressure relief opening is not as likely to be a continuous leak as pressure relief holes located in the fine filter screen or the fine filter body. The vertical portion of the pressure relief tube extends for a height that is less than an upwardly extending drain line of the fluid circulation assembly. Therefore, fluid flows through the open top of the pressure relief tube before flowing through the drain line and out of the dishwasher system, thereby eliminating fluid loss in the tub from fluid flow through the drain line.